Noisy C38 AA supercharger or (bypass valve)

[schulmann]

I have installed a Stage 1 C38 supercharger on my BMW in January. Everything went perfectly and the car has 5000mi more on the counter since this date. In January the weather was cold and I never drove the car with windows down.

However Spring is here. Now I started driving with the windows down and I noticed a strange noise during deceleration.

When the car runs normally or I accelerate (boost) every thing is perfect. When I slow down and lift the gas pedal I can hear a strange noise. It is like a "Spring occilating". I have the impression that the noise is coming from the bypass valve. It sound like the bypass valve can't open continiously to release the excessive boost.

This noise is normal on the bypass valve used by AA ?

Who is the best guy to answer my question at AA ?

[Activ3]

Can you give me a better description of the noise? It's normal for it to sound like its open, hence the continuous whooshing sound on deceleration.

[SammyV]

very vague description of the noise, its going to be really hard to describe im sure, maybe try getting a video but im sure wind noise wil kill it... hopefully you can better describe the noise for activ3
gl

[MachRc]

my ESS kit came with a bosch(i thinks) diverter valve and I switched it to a hyper boost valve..

http://www.stratmosphere.com/hxc_core_2619_combo_logo_48.jpg


http://www.stratmosphere.com/hyperboost.htm

no noises like that under decel, just that diverting whoosh Bah--zzzhheii noise off boost.

[Active Autowerke II]

As has been said before, your description is very vague. Give us a call here, or call me directly at extension 225 and I'll try to get it resolved for you.

[Activ3]

my ESS kit came with a bosch(i thinks) diverter valve and I switched it to a hyper boost valve..

http://www.stratmosphere.com/hxc_core_2619_combo_logo_48.jpg


http://www.stratmosphere.com/hyperboost.htm

no noises like that under decel, just that diverting whoosh Bah--zzzhheii noise off boost.
It's supposed to be partially open under decel. or part throttle, regardless of what brand it is.

I run the AA BOV, but diverted, and it's partially open on part throttle and decel, as all DV's should be with a CF setup.

[MachRc]

^is AA's diverter valve bosch also?

[Activ3]

^is AA's diverter valve bosch also?
The C30 kit uses the bosch valve, and the C38 kit uses the AA Bov.

[02PRUV]

Sounds like his bypass valve might be tightened up a bit too tight maybe?? and it's bouncing open/closed under deceleration instead of holding open. Is this possible??

[schulmann]

It is very difficult to isolate the noise.

Since Monday noise have changed. The temperature dropped from 70F to 40F.
The noise has changed too.


When starting up the car cold there isn't noisy.
Once things warm up a couple of degrees a strong metalic noise starts. It sound like a defectif idle pulley.
Once car gets hot metalic noise transforms into an "oscillation" like noise during deceleration. (Under boost or vacuum) It sounds like "psh, psh psh" :)



After having analyzed things it sounds more like a metalic noise.


I have checked vacuum line. It has a finger sucking vacuum. There is no doubt it is working.
I have check the pulley. They don't seem to have problem, but they are "tight"
I have changed the SC alignment, I reduced the length of the tensioning bar by 1 turn.

[Penn]

Does the sound occur within intervals or is it constant? I had the same "psh psh psh" sound and it turned out to be clogged oil separator line. We took off the oil separator line and it was full of "yellowish goo" (emulsion). After changing the hose the sound disappeared for a week, but then came back.:confused: I booked time to the dealer service so they can take a look at the separator (cyclone) itself. Strangely when i got there next day the sound disappeared again and they couldn't find any faulty parts.:banghead:

[schulmann]

I don't have an oil seperator. I use free air venting. I learned from the past. That yellow staff is deadly for the engin under higher load. In fact once the oil gets into the intake, it gets into the engin. Under higher loads and high rpm it dramatically reduces octan level. From 93 you can drop to 87 !!!! Guess what ? You will hear a big bang and your ring lands will be gone ...

So far everything runs perfectly I am very happy with the kit.

The real difficulty is to adjust the tensioner behind the super charger. Yesterday I over adjusted it by increasing the length of the tensionner by 3 turns. I could see the SC leaning toward the radiator. Then I moved back things. That adjuster seems to be "awkward" but actually it works very well. Once you get used to it (And you find the right wrenches) it is quite easy to adjust it.

I have the impression that this noise is coming from the bypass valve or from the supercharger. It is a constant weak noise under deceleration no matter the boost level. I was wondering if somebody else had this same little noise.

The oil separator was a good guess, but I don't see how it could have made this noise. I think rather disassembling and reassembling the kit made the noise disappear ... I am sure it is a little detail that makes me troubles.

[Active Autowerke II]

The best thing to do is to give us another call at 305-233-9300. I'll get you in touch with one of our engineers and we'll get to the source of the issue.

[2003330i]

its funny that this came up because i just changed mine today to a hyperboost and it makes the same noice under deceleration

[greentrbo95gst]

I am using the turbo xs one
http://www.hirevperformance.net/turboxstypeh341.html

No issues at all.

[schulmann]

I had a lapping day yesterday. This was the first time I used my SC BMW on the track. It was a kind a discovery day to see how the BMW behaves on the track. Guess what ? At the end of the day the noise was gone ... Maybe some parts didn't like the city traffic during the cold winter and got jammed.

So far so good ...

[redronin]

i have the exact same thing going on. although i dont see any mal effects to the car.

its like a very hard fluttering sound, like a turbine is blowing in front of the air being diverted. i dunno if thats accurate but its the best wording i can think up. definitely the diverter. only happens when letting off boost

asa kit, bosch plastic dv

[mikeism]

Hi folks...

In regard to the diverter (bypass) valve noise described as a 'spring that is oscillating' during decelleration... I had a similar issue when I installed a new Stratmosphere HyperBoost diverter valve on my Audi TT Quattro 225. Another description might be something like fluttering peepers that you hear 'peeping' at night near ponds/lakes on a hot summer night. I would hear regular/expected 'whoosh' sound with my windows up, but I was looking for a lake when the windows were down because it sounded like peepers on each decel.

The guys at Stratmosphere.com are great and helped me fix the problem. Turned out to be a vacuum leak in the hose going to the top of the diverter valve. Replaced the hose and the problem was solved. Whoosh with windows down. Whoosh with windows up. No peepers :-)

Mike

[redronin]

Hi folks...

In regard to the diverter (bypass) valve noise described as a 'spring that is oscillating' during decelleration... I had a similar issue when I installed a new Stratmosphere HyperBoost diverter valve on my Audi TT Quattro 225. Another description might be something like fluttering peepers that you hear 'peeping' at night near ponds/lakes on a hot summer night. I would hear regular/expected 'whoosh' sound with my windows up, but I was looking for a lake when the windows were down because it sounded like peepers on each decel.

The guys at Stratmosphere.com are great and helped me fix the problem. Turned out to be a vacuum leak in the hose going to the top of the diverter valve. Replaced the hose and the problem was solved. Whoosh with windows down. Whoosh with windows up. No peepers :-)

Mike

thanks so much for posting your experience, im going to check all vacuum lines tomorrow